The definition of whataboutism is excusing someone’s actions because someone else has done the same. What I’m pointing out here is the opposite.

Whataboutism isn’t excusing; it’s deflecting. To quote from the OED: “The technique or practice of responding to an accusation or difficult question by making a counter-accusation or raising a different issue”

This is exactly what you’ve done.

While whataboutism is definitey toxic to conversation, I've noticed a lot people tend to throw accusations of whataboutism around when they are uncomfortable with their hypocrisy being pointed out.

This is also highly damaging to discourse.